LOS ANGELES 
NBC is looking to revitalize its prime-time lineup with the appointment of a cable TV executive who transformed the once-maligned Showtime channel into a worthy rival to HBO.

Bob Greenblatt, the former Showtime entertainment president who brought pay TV audiences such untested shows as "The Tudors," "Weeds," and "Dexter," was named chairman of NBC Entertainment on Thursday.

Greenblatt's appointment to NBC suggests that cable TV operator Comcast Corp. won't be content to let the network stay in fourth place after it wins federal approval to buy a controlling stake in NBC Universal from General Electric Co., with conditions that regulators are still trying to craft. It also signals that Comcast Chief Operating Officer Steve Burke, a former ABC executive who is taking over as CEO of NBC Universal, will return to investing in new shows in a big way.

The roles won't be effective until the deal closes, expected within the next few months, but Burke said in a statement that "it is important that we are prepared to hit the ground running."

Other top executives will stay in their posts, some with added responsibilities. Bonnie Hammer will remain in charge of cable channels such as USA and Syfy while adding E! and G4, which Comcast now owns. Lauren Zalaznick will continue to oversee Bravo and Oxygen and take on Spanish-language broadcaster Telemundo.

Ted Harbert, a Comcast executive, will join Greenblatt at the broadcast network to oversee its TV stations and deal with station affiliates. Steve Capus will remain head of NBC News, Dick Ebersol will remain atop NBC Sports and Ron Meyer will continue to lead the Universal Studios movie studio.

The most significant change, however, will be at NBC.

The peacock network will get an executive who challenged and surprised fans by getting them to root for a philandering king, a drug-dealing mom and a serial killer.

"Bob took a huge gamble commissioning 'The Tudors,'" Michael Hirst, the show's creator, said in a recent phone interview from Oxford, England.

Hirst noted that Greenblatt got into detailed script conversations about the tale of King Henry VIII, which the BBC had initially turned down. "That's the measure of the guy - that he was prepared to gamble, to trust his instincts on something that the BBC didn't understand."

Greenblatt will take the programming reins at a network that is struggling to right itself from last year's scheduling debacle involving talk show hosts Jay Leno and Conan O'Brien. Last year, NBC moved Leno to 10 p.m., replacing five hours a week of scripted programming with a cheaper talk show. Though bold, the prime-time experiment failed, and to make room for Leno's return to late night, O'Brien left with a big severance package and got his own late-night show on basic-cable channel TBS.

Fourth-ranked NBC said it had ramped up annual program spending about 40 percent this season under outgoing entertainment chairman Jeff Gaspin, though it wouldn't say exactly how much. Yet new shows such as "The Event" were solid singles, not home runs.

The appointment of Greenblatt brings a familiar face to the Hollywood creative community. He produced such award-winning shows as "Six Feet Under" and is someone who worked at the Fox network earlier in his career and understands what mainstream audiences want.

"I feel like it sends a very comforting message," said Darren Star, the creator of the original "Beverly Hills 90210," who worked with Greenblatt when he was executive vice president of prime-time programming at Fox. Greenblatt worked on several successful shows including "The X-Files," "Ally McBeal," and "King of the Hill."

"He's that rare combination of someone who simultaneously understands how to make good old-fashioned commercial television and more sophisticated cable shows and knows the difference," said Star, who also created "Sex and the City" for HBO. "He's made Showtime a very classy, desirable destination. And speaking as somebody who's been working at HBO a lot of years, I certainly respect everything he's done over there."

The appointment brings to a close the era of outgoing NBC Universal CEO Jeff Zucker and a regime that appeared to squeeze the most out of NBC's cash flow while depleting its investment in programming. Zucker and Gaspin said they will leave after Comcast takes over.

Zucker represented an East Coast mentality influenced by majority owner GE, and that didn't always mesh well with Hollywood. Gaspin, who like Zucker also worked on the "Today" show, made his way through the ranks after beginning his career at NBC in finance.

Burke's selection of Greenblatt, a producer and a graduate in theater and arts administration, suggests an embrace of the creative community that wasn't as warm under Zucker.

"My prediction is he will reach out and find people reaching back," said Ted Chervin, the head of worldwide television at talent agency International Creative Management.

Since stepping down amicably from Showtime in July, Greenblatt jumped to the top of the list of people considered to run NBC.

Ratings tend to be cyclical between the networks, and any of them are "a couple of hits away from complete reversal," said writer and creator Tim Kring, whose shows "Heroes" and "Crossing Jordan" each had multiple-year runs at NBC. Bringing in Greenblatt, he said, "sends a message to the creative community that they are hoping to attract creative talent to the network."

That would be a major contrast to NBC's message last year when, in moving Leno to prime time and reducing the number of scripted shows it buys, the network was essentially telling producers to shop their shows elsewhere.

But Greenblatt also comes into a difficult situation for any executive tasked with programming about 20 hours of shows every week. Broadcasters tend to launch dozens of new shows in September, not all of which succeed. That's a trend which manifested itself again this year as NBC canceled "Undercovers" and "Outlaws" but renewed "30 Rock" for a sixth season, through 2012.

Rick Feldman, the president of the National Association of Television Program Executives, said Greenblatt's background at Showtime, where shows are launched in periods other than the fall, could help dislodge the scheduling logjam. "Perhaps because of his experience, he could be one of the people that would be able to change the system."

Fans of NBC are hoping he can guide it out of trouble.

"He's the perfect mix of incredible creative instincts with total business acumen," said David Janollari, the head of programming at MTV who helped run Greenblatt Janollari Studio, which created "Six Feet Under." Janollari watched from afar as Greenblatt took Showtime, which lagged HBO, and turned it around in just a few years. NBC is "lucky to have him," he said. "I really feel they have nowhere to go but up."